12V landscape lighting transformers - Maximum distance

I want to place a low voltage transformer on the outside wall of my house to power my 12V landscape lights on the lawn. However, the lights on the lawn will range in distance from 10ft to about 200 feet from the transformer. I heard there was some maximum distance limitation for low voltage transformers. Can anyone direct me to reliable information on this limitation. I figure I will need about a 800Watts transformer, but am worried about the 200foot maximum distance. Thanks in advance for your replies.

Your Main concern will be the voltage drop of the system. As the distance of copper wire increases, it increases in resistance. This causes voltage to decrease the longer the cable run. The way to compensate for the loss is to increase the wire size. Larger wire has better conductivity => less resistance.

The following site shows the size wire you will need to keep your 12V all the way to the 200'. It is based on the power of the system.